Page:Practical Treatise on Milling and Milling Machines.djvu/205

Rh Cutting a Spiral with End Mill

When a spiral slot with parallel sides is required an end mill should be employed and the job set up as shown above.

The spiral head centres are brought to a level with the centre of the machine spindle.

The table is at right angles to the spindle and the angle of the spiral is obtained by the combination of change gears used.

Either right or left-hand spirals can be cut in this way by simply leaving out or interposing an intermediate gear in the train of change gears.